Automobile panel-shaped parts have a large problem concerning weight reduction thereof, and molded products obtained from fiber-reinforced plastics tend to be used for the panel-shaped parts in place of steel plates. Various studies on automobile windows such as sunroof windows, quarter windows, rear windows, seethrough windows for front passenger seats of trucks have also been made to utilize panel-shaped molded products having a light weight and an excellent design property.
As the panel-shaped molded products, there have been proposed, for example, “two-color molded products” having a two-layer structure as shown in FIG. 11. FIG. 11 is a vertical cross-sectional view partially showing a layer structure of a window frame part of a conventional panel-shaped molded product used as windows for automobiles in which a member represented by reference numeral (1) denotes a window glass formed from a resin, a member represented by reference numeral (2) denotes a window frame, and a member represented by reference numeral (3) denotes an opening defining the window. The panel-shaped molded product as shown in FIG. 11 comprises a design part (1) (transparent portion) of a plate shape which is formed from a transparent resin and constitutes a window glass, and a frame part (2) which is formed from an opaque reinforced resin to which an inorganic filler such as glass fibers and talc is added as a reinforcing material, and constitutes a window frame. These parts of the panel-shaped molded product are integrally laminated with each other by injection molding method (two-color molding or co-injection molding method) (Patent Documents 1 and 2).
The two-color molding method is contemplated to enhance a production efficiency and ensure a beautiful appearance of finished molded products. When producing the above panel-shaped molded product by the two-color molding method, the first material to which the reinforcing material is added is first injected to form the frame part (2), and then the second material (transparent resin) is injected to form the design part (1), so that a residual stress in the design part (1) is reduced to prevent occurrence of deformation such as curvature and waviness thereon. That is, in the two-color-part molding method, the frame part (2) is first injection-molded, and then after allowing a strong shrinkage phenomenon of the frame part to proceed to some extent, the design part (1) is injection-molded, thereby preventing the design part (1) from being adversely influenced by the shrinkage of the frame part (2).
Patent Document 1: Japanese Patent Application Laid-Open (KOKAI) No. 2003-320548
Patent Document 2: Japanese Patent Application Laid-Open (KOKAI) No. 2005-013907